Geographically dispersed transceiver sites are often employed in two-way radio communication systems to support subscribers operating over a wide coverage area. Ordinarily, the sites are arranged such that each provides coverage for a particular geographic region, which may have some overlap. A subscriber unit interfaces with a radio communication system through a particular transceiver site, referred to herein as a server site or cell site. When a subscriber unit moves from one location to another, it may be advantageous to switch site affiliation, such as to a neighboring site, in order to ensure a high quality communication link. Prior to switching site affiliation, a subscriber unit usually monitors communications from potential server sites in order to select a suitable site server site.
A particular problem may occur when a subscriber unit initiates the switching of affiliation from one site to another, in that there is a possibility of missing incoming calls. Consider a subscriber unit that is affiliated with a first site in a radio communication system. The radio system routes calls destined for the subscriber unit via that site. The subscriber unit may switch affiliation to a second site by obtaining particular information from the second site for setup and registration purposes, and by registering affiliation with the second site. Upon detection of this change in site affiliation, the radio system is alerted to route calls destined for the subscriber unit through the second site. Although the process to switch site affiliation may take but a few seconds, a problem exists in prior systems employing this method in that calls may be lost during the transition from the first site to the second site.
It is desirable to provide an enhanced procedure for changing site affiliation that reduces the potential of lost calls. Therefore, a new method of processing a call while switching site affiliation in a radio communication system is needed.